Electronic device comprising an electronic chip mounted on top of a support substrate

ABSTRACT

A support substrate has a mounting face with a metal heat transfer layer. Holes are provided to extend at least partially through the metal heat transfer layer. Metal heat transfer elements are disposed in the holes of the metal heat transfer layer of the support substrate. An electronic integrated circuit (IC) chip has a rear face that is fixed to the mounting face of the support substrate via a layer of adhesive material. The metal heat transfer elements disposed in the holes of the metal layer of the support substrate extend to protrude, relative to the mounting face of the support substrate, into the layer of adhesive material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/889,112, filed Jun. 1, 2020, which claims the priority benefit ofFrench Application for Patent No. 1905858, filed on Jun. 3, 2019, thecontents of which are hereby incorporated by reference in theirentireties to the maximum extent allowable by law.

TECHNICAL FIELD

The present invention relates to the field of the electronic devicesthat comprise integrated circuit (IC) chips mounted on supportsubstrates.

BACKGROUND

In the case where the IC chips produce heat, it is advantageous totransfer a portion of the heat produced to the support substrates.

SUMMARY

According to one embodiment, an electronic device is proposed whichcomprises a support substrate having a facing mounting face and anelectronic chip of which a rear face is fixed onto the facing mountingface of the support substrate via a layer of an adhesive material (suchas a glue).

The support substrate includes a metal heat transfer layer on the sideof its mounting face, opposite the chip, and having a plurality ofholes.

The electronic device further comprises a plurality of metal heattransfer elements disposed in the holes of the metal layer of thesupport substrate and extending protruding, relative to the mountingface of the support substrate, into the layer of adhesive material.

Thus, the transfers of heat between the chip and the support substrateare increased.

The support substrate and the chip can advantageously be free ofelectrical connections via the metal heat transfer layer and the metalheat transfer elements.

The heat transfer elements can be at a distance from the rear face ofthe chip.

The support substrate can include an integrated network of electricalconnections having front electrical connection blocks on the side of thefacing mounting face of the support substrate, electrical connectionmeans linking the chip and the front blocks of the network of electricalconnections of the support substrate.

The metal heat transfer layer and the front electrical connection blockscan be disposed in one and the same metal level of the supportsubstrate.

The electrical connection means can comprise metal wires linking frontblocks of the support substrate and front blocks of a front face of thechip.

The device can comprise an encapsulation block on top of the facing faceof the support substrate, in which the chip and the electricalconnection means are embedded.

Also proposed is a method for fabricating an electronic device, whichcomprises the following steps: obtaining a support substrate having amounting face and including a metal heat transfer layer on the side ofthis mounting face; producing holes in the metal heat transfer layer;placing metal heat transfer elements in the holes of the metal heattransfer layer, the metal heat transfer elements extending protrudingrelative to the mounting face of the support substrate; performing abrazing heat treatment of the metal heat transfer elements in the holesof the metal heat transfer layer; depositing a layer of adhesivematerial on top of the mounting face of the support substrate, in whichthe protruding parts of the heat transfer elements protruding relativeto the mounting face of the support substrate are embedded; and placingan electronic integrated circuit (IC) chip on top of the layer ofadhesive material so as to fix the chip on top of the support substrate.

The method can comprise the following subsequent step: placingconnection wires between the IC chip and the support substrate.

The method can comprise the following subsequent step: producing anencapsulation block on top of the support substrate, in which the ICchip is embedded.

BRIEF DESCRIPTION OF THE DRAWINGS

An electronic device will now be described by way of non-limitingexemplary embodiment, illustrated by the drawing in which:

FIG. 1 shows a cross section of an electronic device;

FIG. 2 shows a step of fabrication of the electronic device of FIG. 1 ;

FIG. 3 shows a subsequent step of fabrication of the electronic deviceof FIG. 1 ;

FIG. 4 shows a subsequent step of fabrication of the electronic deviceof FIG. 1 ;

FIG. 5 shows a subsequent step of fabrication of the electronic deviceof FIG. 1 ;

FIG. 6 shows a subsequent step of fabrication of the electronic deviceof FIG. 1 ; and

FIG. 7 shows a subsequent step of fabrication of the electronic deviceof FIG. 1 .

DETAILED DESCRIPTION

An electronic device 1 illustrated in FIG. 1 comprises a supportsubstrate 2 which has a mounting face 3 and a rear face 4 and anelectronic integrated circuit (IC) chip 5 having a rear face 6 that isfixed onto the mounting face 3 of the support substrate via a layer ofan adhesive material (such as glue) 7.

The support substrate 2 is provided with a metal heat transfer layer 8which is attached to the support substrate 2 on the side of its mountingface 3, and which extends opposite at least a part of the rear face 6 ofthe IC chip 5 and which possibly extends beyond at least a part of theperipheral edge of the IC chip 5. Advantageously, the metal heattransfer layer extends opposite the entire rear face 6 of the IC chip 5and beyond the entire periphery of the IC chip 5.

The metal layer 8 at the mounting face of the support substrate 2 has aplurality of holes 9 which are opposite and open on the side of the rearface 6 of the IC chip 5. The holes 9 can be produced to extend onlypartially though the thickness of the metal layer 8 or extend completely(entirely) through the thickness of the metal layer 8.

The electronic device 1 comprises a plurality of metal heat transferelements 10, in the approximate form of balls, which are fitted into theholes 9 of the metal layer 8 and which include a portion that protrudesrelative to the facing face 3 of the support substrate 2 so that theprotruding parts of the heat transfer elements extend above the uppersurface of the metal layer and are embedded in the layer of adhesivematerial 7.

The heat transfer elements 10 include a portion which at least partiallyfills the holes 9 and are linked (attached) to the metal layer 8 bybrazing. Advantageously, the top surfaces of the heat transfer elements10, which in an embodiment present an outer domed surface shape, arespaced at a distance from the rear face 6 of the IC chip 5.

The support substrate 2 and the IC chip 5 are free of electricalconnections via the metal heat transfer layer 8 and the metal heattransfer elements 10. The heat transfer elements 10 therefore have noelectrical connection function between the IC chip 5 and the supportsubstrate 2.

A portion of the heat produced by the IC chip 5 is transferred to thesupport substrate 2 via the layer of adhesive material 7. By virtue ofthe existence of the metal heat transfer layer 8 and of the metal heattransfer elements 10, the flow of heat between the IC chip 5 and thesupport substrate 2 is considerably increased.

The holes 9 and consequently the metal heat transfer elements 10 can beevenly distributed or, possibly, be more dense in the zone or zones ofthe IC chip 5 that produce the most heat.

The support substrate 2 is provided with an integrated network ofelectrical connections 11 which is linked to the IC chip 5 by electricalconnection means 12 (provided, for example, in the form of bondingwires).

The metal heat transfer layer 8 and the metal heat transfer elements 10on the one hand and the integrated network of electrical connections 11and the electrical connection means 12 on the other hand are distinct.

According to a variant embodiment, the integrated network of electricalconnections 11 comprises front electrical connection blocks 13 on theside of the facing face 3 of the support substrate 2. The front blocksare formed beyond and at a distance from the peripheral edge of the ICchip 5 and at a distance from the metal heat transfer layer 8.

The electrical connection means 12 comprise electrical wires 14 whichlink the front electrical connection blocks 13 and front electricalconnection blocks 15 of the front face 16 of the IC chip 5.

The integrated network of electrical connections 11 comprises rearelectrical connection blocks 17 on the side of the rear face 4 of thesupport substrate 2, in order to connect the IC chip 5 to the outside.

Advantageously, the metal heat transfer layer 8 and the front electricalconnection blocks 13 are formed in one and the same metal level of thesupport substrate 2. In this configuration, top surfaces of the metalheat transfer layer 8 and front electrical connection blocks 13 may becoplanar with surface 3 of the substrate 2. The metal heat transferelements 10 extend above this coplanar surface.

The result of the above is that, in light of the mounting of the IC chip5 on the support substrate 2 and of the electrical connection means 12between the IC chip 5 and the support substrate 2, the metal layer 8 andthe elements 10 constitute additional, exclusively heat-transferoriented means.

The electronic device 1 further comprises an encapsulation block 18 ontop of the facing face 3 of the support substrate, in which the chip 5and the electrical wires 14 are embedded.

The electronic device 1 can be fabricated as follows.

As illustrated in FIG. 2 , a support substrate 2 is obtained that isprovided with the metal heat transfer layer 8 and the network ofelectrical connections 11.

In a fabrication step illustrated in FIG. 3 , the holes 9 are producedin the metal heat transfer layer 8, by drilling or etching.

In a subsequent fabrication step illustrated in FIG. 4 , the metal heattransfer elements 10 are placed in the holes 9.

In a subsequent fabrication step illustrated in FIG. 5 , a heattreatment is performed, for example in an oven, so as to fix the metalheat transfer elements 10 by brazing to the metal heat transfer layer 8.In response to the heat treatment, the material forming the metal heattransfer elements 10 creeps so as to, advantageously, provide a portionwhich fills the holes 9 and provide another portion which protrudes fromthe holes.

In a subsequent fabrication step illustrated in FIG. 6 , the layer ofadhesive material (for example, glue) 7 is deposited, the protrudingportions of the metal heat transfer elements 10 then being embedded inthis layer of adhesive material 7.

In a subsequent fabrication step illustrated in FIG. 7 , the IC chip 5is placed on top of the layer of adhesive material 7 and the adhesivematerial is hardened so as to fix the IC chip 5 on top of the supportsubstrate 2. Then, the electrical connection wires 14 are put in place.

Finally, the encapsulation block 18 is formed.

The electronic device 1 is then obtained.

1. A method for fabricating an electronic device, comprising: producinga metal heat transfer layer at a mounting face of a support substrate;forming holes in the metal heat transfer layer; placing metal heattransfer elements in the holes of the metal heat transfer layer, themetal heat transfer elements extending to protrude above the mountingface of the support substrate; performing a brazing heat treatment tosecure the metal heat transfer elements in the holes of the metal heattransfer layer; depositing a layer of adhesive material on top of themounting face of the support substrate, wherein protruding parts of themetal heat transfer elements extend to protrude, relative to themounting face of the support substrate, to be embedded within the layerof adhesive material; and placing an electronic integrated circuit (IC)chip on top of the layer of adhesive material so as to fix the IC chipon top of the support substrate.
 2. The method according to claim 1,further comprising placing electrical connection wires between the ICchip and the support substrate.
 3. The method according to claim 1,further comprising producing an encapsulation block on top of thesupport substrate, in which the IC chip is embedded.
 4. The methodaccording to claim 1, wherein surfaces of said protruding parts of themetal heat transfer elements are spaced by a distance from a rear faceof the IC chip.
 5. The method according to claim 1, wherein an uppersurface of the metal heat transfer layer is coplanar with the mountingface of the support substrate.
 6. The method according to claim 1,wherein the holes extend completely through the metal heat transferlayer.
 7. The method according to claim 1, wherein the adhesive materialis glue.
 8. A method for fabricating an electronic device, comprising:obtaining a support substrate having a facing mounting face andincluding a metal heat transfer layer on the facing mounting face;producing holes in the metal heat transfer layer; placing metal heattransfer elements in the holes of the metal heat transfer layer; whereinsaid metal heat transfer elements protrude above the facing mountingface of the support substrate; heat treating the metal heat transferelements in the holes of the metal heat transfer layer depositing alayer of glue over the facing mounting face of the support substrate;wherein said layer of glue embeds parts of the heat transfer elementswhich protrude above to the facing mounting face; placing an electronicintegrated circuit chip over the embedded parts of the heat transferelements; wherein said electronic integrated circuit chip is in contactwith said layer of glue so as to affix the electronic integrated circuitchip to the support substrate.
 9. The method of claim 8, wherein heattreating comprises performing a brazing heat treatment of the metal heattransfer elements in the holes of the metal heat transfer layer;
 10. Themethod of claim 8, further comprising, after placing the electronicintegrated circuit chip, connecting electrical connection wires betweenthe electronic integrated circuit chip and the support substrate. 11.The method of claim 8, further comprising, after placing the electronicintegrated circuit chip, producing an encapsulation block over thesupport substrate and which encapsulates the electronic integratedcircuit chip.
 12. The method of claim 8, wherein surfaces of said partsof the heat transfer elements which protrude above to the facingmounting face are spaced by a distance from a rear face of theelectronic integrated circuit chip.
 13. The method of claim 8, whereinan upper surface of the metal heat transfer layer is coplanar with themounting face of the support substrate.
 14. The method of claim 8,wherein the holes extend completely through the metal heat transferlayer.